# Alloy 690 Forgings (UNS N06690)

UNS N06690 / W.Nr. 2.4642 / NiCr29Fe / ASTM B564

Published by Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory, Jiangyin, Jiangsu, China.
Last reviewed 13 August 2026.
Source page: https://www.steelforgepieces.com/Nickel-Alloy/ALLOY-690.html

## Summary

Alloy 690 is a nickel-chromium-iron alloy with 58% nickel minimum and 27-31% chromium. Its UNS number is N06690 and its Werkstoff number is 2.4642. The high chromium content gives resistance to stress-corrosion cracking in high-purity water, to nitric and nitric/hydrofluoric acid, and to oxidation and sulfidation at high temperature. It is the standard material for nuclear steam generator tubing, tube sheets and internals.

Jiangyin Jiangnan Metal Co., Ltd. forges Alloy 690 to ASTM B564 and ASTM B166. Forms include seamless rolled rings, forged rings, flanges, round bars, discs, bushings, sleeves, tube sheets, shafts and pipes. Material is ESR refined and supplied solution annealed with an EN 10204 3.1 or 3.2 certificate.

## Key data

| Item | Value |
|---|---|
| UNS number | N06690 |
| Werkstoff number | 2.4642 |
| Other names | Inconel 690, Nicrofer 6030 |
| Alloy family | Ni-Cr-Fe (NiCr29Fe) |
| Nickel | 58% min |
| Chromium | 27.0-31.0% |
| Forging specification | ASTM B564 / ASME SB-564 |
| Bar specification | ASTM B166 / ASME SB-166 |
| Tensile strength Rm | 586 MPa min |
| Yield strength Rp0.2 | 241 MPa min |
| Elongation A | 30% min |
| Density | 8.2 g/cm3 |
| Melting range | 1390-1410 C |
| Solution anneal | 1040 C approx. |
| Melt route | EAF + VOD + ESR |
| Certification | EN 10204 3.1 / 3.2 |

## What is Alloy 690

Alloy 690 is a solid-solution nickel-chromium-iron alloy for oxidizing service. Chromium is held at 27-31%, about double the level in Alloy 600. The chromium forms a stable Cr2O3 passive film. That film is what allows the alloy to work in nitric acid, in mixed nitric and hydrofluoric pickling baths, in hot caustic, and in oxidizing gases at high temperature.

Nickel is 58% minimum. It keeps the structure austenitic and non-magnetic across the full temperature range and provides resistance to chloride stress-corrosion cracking and to sodium hydroxide. Iron is specified at 7-11% as a matrix element.

Alloy 690 is not precipitation hardened, so it does not lose properties through overaging and it holds its structure over long exposures. That is why it was selected to replace Alloy 600 after Alloy 600 steam generator tubing suffered primary water stress-corrosion cracking in pressurized water reactors.

### Equivalent designations

| System | Designation |
|---|---|
| UNS | N06690 |
| Werkstoff (W.Nr.) | 2.4642 |
| EN chemical symbol | NiCr29Fe |
| Trade names | INCONEL 690, Nicrofer 6030, VDM Alloy 690 |
| Shorthand | Alloy 690, 690, 690TT (thermally treated) |

INCONEL is a registered trademark of Special Metals Corporation. Jiangyin Jiangnan Metal Co., Ltd. supplies this material under the generic designation Alloy 690 / UNS N06690.

## Chemical composition

ASTM B166 and ASTM B564 limits for UNS N06690, weight %.

| Element | Symbol | Minimum | Maximum |
|---|---|---|---|
| Nickel | Ni | 58.0 | balance |
| Chromium | Cr | 27.0 | 31.0 |
| Iron | Fe | 7.0 | 11.0 |
| Carbon | C | | 0.05 |
| Silicon | Si | | 0.50 |
| Manganese | Mn | | 0.50 |
| Copper | Cu | | 0.50 |
| Sulfur | S | | 0.015 |

Nuclear procurement specifications often tighten carbon, sulfur and trace elements such as cobalt, boron and nitrogen beyond the ASTM limits.

## Mechanical properties

Room temperature minima, solution annealed condition.

| Property | Symbol | Bar, ASTM B166 | Forging, ASTM B564 |
|---|---|---|---|
| Tensile strength | Rm | 586 MPa min (85 ksi) | 586 MPa min (85 ksi) |
| 0.2% proof strength | Rp0.2 | 241 MPa min (35 ksi) | 241 MPa min (35 ksi) |
| Elongation | A | 30% min | 30% min |

Mill results normally exceed these minima. Hardness in the solution annealed condition typically falls between 75 and 95 HRB.

## Physical properties

| Property | Value | Condition |
|---|---|---|
| Density | 8.2 g/cm3 (0.296 lb/in3) | 20 C |
| Melting range | 1390-1410 C | |
| Modulus of elasticity | 212 GPa (30.8 x 10^3 ksi) | 20 C |
| Electrical resistivity | 116 micro-ohm cm | 20 C |
| Specific heat | 496 J/(kg K) | 100 C |
| Thermal conductivity | 13.9 W/(m K) | 100 C |
| Mean thermal expansion | 13.7 x 10^-6 /K | 20-100 C |
| Relative magnetic permeability | 1.01 max | 20 C |

Values taken from published producer data for UNS N06690 (VDM Metals, February 2021 edition). Producer data sheets differ slightly, in particular on melting range.

## Applicable standards

| Product form | ASTM | ASME |
|---|---|---|
| Forgings | ASTM B564 | ASME SB-564 |
| Rod, bar and wire | ASTM B166 | ASME SB-166 |
| Plate, sheet and strip | ASTM B168 | ASME SB-168 |
| Seamless pipe and tube | ASTM B167 | ASME SB-167 |
| Welded tube | ASTM B163 | ASME SB-163 |
| Ultrasonic testing | ASTM A388 | EN 10228-3, SEP 1921 |
| Material certificate | | EN 10204 3.1 / 3.2 |

## Forged products

Jiangyin Jiangnan Metal Co., Ltd. produces the following in Alloy 690, all to customer drawing:

- Seamless rolled rings
- Forged rings
- Flanges: weld neck, slip on, blind, custom profiles
- Round bars, forged and peeled or turned
- Discs and disks, solid or bored
- Tube sheets for heat exchangers and steam generators
- Shafts and spindles for pumps, compressors and turbines
- Sleeves and bushings
- Pipes, tubes and forged hollows
- Valve parts: stems, seat rings, bodies, blocks
- Nozzles, set-on and set-in
- Gear blanks

Alloy 690 forgings are made to drawing. Send the finished and rough dimensions together with the single piece weight for confirmation. Minimum order is one piece.

## Manufacturing route

1. **Melting and refining.** The heat is melted in an electric arc furnace, refined by vacuum oxygen decarburization to bring carbon and sulfur down, then remelted by electroslag remelting. ESR gives the inclusion cleanliness and ingot homogeneity required for nuclear and pressure vessel work.
2. **Ingot heating.** Ingots are soaked at 1100 to 1200 C on a controlled ramp. The high chromium matrix does not tolerate thermal shock.
3. **Open-die forging or ring rolling.** Billets are upset, drawn and punched on hydraulic open-die presses, or expanded on a ring mill for seamless rolled rings. Finish temperature is held above 950 C. Alloy 690 work hardens quickly, so the pass schedule allows for adequate reductions and reheats.
4. **Solution annealing.** Forgings are solution annealed at about 1040 C and cooled rapidly. This dissolves chromium carbides at the grain boundaries and restores corrosion resistance.
5. **Thermal treatment for 690TT.** Where specified, a further treatment near 715 C for 10 to 15 hours precipitates semi-continuous intergranular carbides and improves resistance to primary water stress-corrosion cracking.
6. **Machining and non-destructive testing.** Parts are rough machined, then ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 at the acceptance class specified.
7. **Certification and dispatch.** Chemistry, mechanical results and the dimensional report are issued on an EN 10204 3.1 certificate, or 3.2 with third party witness.

## Applications

**Nuclear power.** Steam generator tube sheets, channel head components, divider plates, tube support internals, baffles, control rod drive mechanism parts and reactor coolant system hardware. Alloy 690TT is the reference material for replacement steam generators.

**Nitric acid and nuclear fuel reprocessing.** Tail gas reheaters in nitric acid plants, heating coils and tanks for nitric and hydrofluoric pickling solutions, dissolver vessels and reprocessing hardware.

**Chemical and petrochemical processing.** Forged flanges, valve bodies, stems, seat rings, pump shafts, tube sheets and nozzles for reactors, columns, towers, silos, preheaters and shell and tube heat exchangers.

**High temperature service.** Furnace retorts, muffles, radiant tubes, thermowells and heat treatment fixtures, and components exposed to sulfur bearing atmospheres in coal gasification and waste incineration.

**Waste vitrification.** Melter components and hardware in nuclear waste vitrification plants.

## Alloy 690 compared with Alloy 600 and Alloy 800H

| Property | Alloy 690 | Alloy 600 | Alloy 800H |
|---|---|---|---|
| UNS | N06690 | N06600 | N08810 |
| Nickel | 58% min | 72% min | 30-35% |
| Chromium | 27-31% | 14-17% | 19-23% |
| Iron | 7-11% | 6-10% | balance |
| SCC in pure water | excellent | poor | moderate |
| Oxidizing acid | excellent | moderate | moderate |
| Creep strength | moderate | moderate | high |
| Relative cost | high | high | lower |
| Typical use | nuclear SG, nitric acid | legacy nuclear, furnaces | creep service, reformers |

Alloy 690 is selected where stress-corrosion cracking or oxidizing acid attack governs. Alloy 800H is selected where long term creep strength at temperature governs. Alloy 600 is now largely a legacy specification for water service because of its PWSCC record.

## Testing and certification

- Chemical analysis, full heat analysis, with product analysis on request
- Mechanical testing: tensile, yield and elongation at room temperature, elevated temperature and impact testing where specified
- Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388
- Liquid penetrant inspection on machined surfaces
- Intergranular corrosion testing to ASTM A262 or equivalent
- Dimensional report against drawing before dispatch
- EN 10204 3.1 certificate as standard, or EN 10204 3.2 witnessed by TUV, SGS, BV, Lloyd's or the customer's inspector

## How to order

Send the following to sales@steelforgepieces.com:

1. Drawing, or finished and rough dimensions with tolerances
2. Specification and grade, for example ASTM B564 UNS N06690
3. Delivery condition: solution annealed, or 690TT
4. Quantity and required delivery date
5. Certificate level: EN 10204 3.1 or 3.2
6. NDT and third party inspection requirements, if any
7. Destination port for the freight quotation

Quotations are returned within one working day.

## Questions and answers

**What is Alloy 690?**
Alloy 690 is a nickel-chromium-iron alloy with 58% nickel minimum and 27-31% chromium. Its UNS number is N06690 and its Werkstoff number is 2.4642. The high chromium content gives resistance to oxidizing acids, to oxidation at high temperature, and to stress-corrosion cracking in high-purity water. It is the standard material for nuclear steam generator tubing, tube sheets and internals.

**Is Alloy 690 the same as Inconel 690?**
The chemistry and the specification are the same. INCONEL 690 is the trade name of Special Metals Corporation. Alloy 690 is the generic designation for the same UNS N06690 composition, sold by other producers as Nicrofer 6030 or VDM Alloy 690. All meet the same ASTM B166 and ASTM B564 limits. Jiangyin Jiangnan Metal Co., Ltd. supplies the material as Alloy 690 / UNS N06690.

**What is the chemical composition of Alloy 690?**
Alloy 690 (UNS N06690) contains nickel 58% minimum, chromium 27.0-31.0%, iron 7.0-11.0%, carbon 0.05% maximum, silicon 0.50% maximum, manganese 0.50% maximum, copper 0.50% maximum and sulfur 0.015% maximum.

**What are the mechanical properties of Alloy 690 forgings?**
In the solution annealed condition, Alloy 690 bar and forgings to ASTM B166 and ASTM B564 meet minimum values of tensile strength Rm 586 MPa (85 ksi), 0.2% proof strength Rp0.2 241 MPa (35 ksi) and elongation A 30%. Mill results normally exceed these minima and are certified per heat.

**Which standards cover Alloy 690 forgings?**
ASTM B564 and ASME SB-564 cover nickel alloy forgings. ASTM B166 and ASME SB-166 cover rod, bar and wire. ASTM B168 covers plate, sheet and strip. ASTM B167 and B163 cover pipe and tube. Jiangyin Jiangnan Metal Co., Ltd. normally delivers Alloy 690 forgings to ASTM B564.

**Why is Alloy 690 used instead of Alloy 600 in nuclear steam generators?**
Alloy 690 holds about 29% chromium against about 15.5% in Alloy 600. The higher chromium level improves resistance to primary water stress-corrosion cracking, which caused extensive steam generator tube degradation in plants built with Alloy 600. Since the 1980s, Alloy 690 in the thermally treated 690TT condition has been the replacement material.

**What is the difference between Alloy 690 and Alloy 690TT?**
The composition is the same and the temper differs. Alloy 690 is supplied solution annealed at about 1040 C followed by rapid cooling. Alloy 690TT receives a further thermal treatment near 715 C for 10 to 15 hours, which precipitates semi-continuous chromium carbides along the grain boundaries and improves resistance to primary water stress-corrosion cracking. TT material is normally specified for nuclear service.

**How is Alloy 690 forged and heat treated?**
Alloy 690 is hot worked from 1100 to 1200 C with the finish temperature held above 950 C. It work hardens quickly, so the pass schedule allows for adequate reductions and reheats. After forging, parts are solution annealed at about 1040 C and cooled rapidly to dissolve chromium carbides and restore corrosion resistance.

**Can Alloy 690 be welded?**
Yes. It is welded by GTAW and plasma processes. The material should be solution annealed, clean and free of scale, grease and marking ink before welding. Against carbon steel it has lower thermal conductivity and higher thermal expansion, and the weld metal is more viscous, so root gaps of 1 to 3 mm and included angles of 60 to 70 degrees are usual, with pure argon root shielding.

**Is Alloy 690 magnetic?**
No. Alloy 690 is austenitic and essentially non-magnetic, with a relative magnetic permeability of 1.01 or less at 20 C.

**What forged shapes of Alloy 690 can be supplied?**
Jiangyin Jiangnan Metal Co., Ltd. produces Alloy 690 seamless rolled rings, forged rings, flanges, round bars, discs and disks, bushings, sleeves, tube sheets, shafts, spindles, hollow forgings, pipes, tubes, nozzles, blocks and valve components including stems, seat rings and bodies, all to customer drawing.

**What testing and certification is supplied with Alloy 690 forgings?**
Every order carries chemical analysis and mechanical test results on an EN 10204 3.1 certificate, or EN 10204 3.2 with third party witness such as TUV, SGS, BV or Lloyd's. Ultrasonic testing is done to EN 10228-3, SEP 1921 or ASTM A388 as specified. Liquid penetrant, hardness testing and intergranular corrosion testing are available on request.

**Who supplies Alloy 690 forgings in China?**
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. It produces Alloy 690 (UNS N06690) forged rings, flanges, bars, discs, shafts and tube sheets for export worldwide. Contact sales@steelforgepieces.com or +86-189-2135-9659.

**What information is needed to quote Alloy 690 forgings?**
Send the drawing or the finished dimensions, the specification such as ASTM B564, the delivery condition (solution annealed or 690TT), the quantity, the certificate level (EN 10204 3.1 or 3.2), and any non-destructive testing or third party inspection requirement. Quotations are returned within one working day.

## About the manufacturer

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. The works produces forged rings, seamless rolled rings, flanges, round bars, discs, shafts, sleeves, tube sheets and valve components in carbon steel, alloy steel, tool steel, stainless steel and nickel alloys.

Forgings are made to customer drawing, heat treated in house, ultrasonically tested to European or ASTM acceptance standards, and released against an EN 10204 3.1 or 3.2 certificate. The company exports to Europe, North America, the Middle East, Southeast Asia and Australia.

## Reference standards

- ASTM B564, Standard Specification for Nickel Alloy Forgings
- ASTM B166, Standard Specification for Nickel-Chromium-Iron Alloys Rod, Bar and Wire
- ASME Boiler and Pressure Vessel Code, Section II Part B, SB-564 and SB-166
- EN 10228-3, Non-destructive testing of steel forgings, ultrasonic testing
- EN 10204, Metallic products, types of inspection documents
- SEP 1921, Ultrasonic testing of steel forgings
- ASTM A388, Standard Practice for Ultrasonic Examination of Steel Forgings
- VDM Metals, VDM Alloy 690 Nicrofer 6030 material data sheet, February 2021

## Document reference

Alloy 690 Forgings (UNS N06690): Composition, Properties and Manufacturing.
Issued by Jiangyin Jiangnan Metal Co., Ltd., No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China 214423.
Reviewed 13 August 2026. https://www.steelforgepieces.com/Nickel-Alloy/ALLOY-690.html
Enquiries: sales@steelforgepieces.com, +86-189-2135-9659.